1. Field of the Invention
The present invention relates to a semiconductor for electric power used in electric vehicles and so on, in particular to a structure of a main circuit terminal which is outwardly introduced.
2. Discussion of Background
A semiconductor device for electric power as an intelligent power module (IPM) used to control to drive an electric vehicle is required to have a small size, compactness, a long-lifetime under severe circumstances in terms of temperature, vibration, and so on, and high reliability. A conventional semiconductor device for electric power will be described in reference of FIGS. 11 through 14.
In FIGS. 11 and 12, numerical reference 1 designates a resin case; numerical reference 2 designates a main circuit terminal inserted in the resin case 1; numerical reference 2a designates an end of the main circuit terminal connecting to an outside and exposed on an outer surface of the resin case 1; and numerical reference 2b designates an end of the main circuit terminal 2 connected to an inside and exposed to an inner surface of the resin case 1. The main circuit terminal 2 is bent at substantially right angles so that a part of the end 2a of the main circuit terminal 2 on the side of connecting to the outside is in parallel to an outwardly exposed resin surface 1a of the resin case 1. Further, numerical reference 3 designates a metallic base plate forming a bottom portion of the resin case 1; numerical reference 4 designates a cover made of a resin; numerical reference 5 designates a connector for a signal circuit, which connector is mounted on a control board 11, described below; and numerical reference 6 designates a signal circuit terminal located in the control board 11. References (P) and (N), affixed to the end 2a of the main circuit terminal 2 for outwardly connecting, respectively designate an input of a positive electricity and an input of a negative electricity. References (U), (V), and (W) designate three phases, i.e. a U-phase, a V-phase, and a W-phase.
Numerical reference 7 designates a nut. The nut 7 is inserted in a hexagonal hole 1b previously formed at time of molding to receive the nut and covered by the end 2a on the outwardly connecting side. The insulating substrate 8 is mounted on the metallic base plate 3 forming a bottom portion of the resin case 1, a semiconductor element for electric power 9 is mounted on the insulating substrate 8, and the end 2b of the main circuit terminal 2 on the inwardly connecting side is connected to the semiconductor element for electric power 9 by an aluminum wire 10. Numerical reference 11 designates the control board, on which the connector 5 for the signal circuit is mounted. On the control board, controlling parts 12 are mounted, and the controlling parts 12 are connected to the semiconductor element for electric power 9 through a relay terminal for signal 13. The insulating substrate 8, the semiconductor element for electric power 9, and so on are sealed by a gel-like sealing resin 14.
In the following discussion, in reference of FIG. 13, details of a structure of the end 2a on the outwardly connecting side in the main circuit terminal 2 and a method of assembling the same will be described. In FIG. 13, after embedding the nut 7 in the hole 1b formed in the resin case 1, the end 2a on the outwardly connecting side is bent at substantially right angles in a bending portion 2e so that the end 2a on the outwardly connecting side covers the nut 7, whereby an outer surface 2c and an inner surface 2d of the end 2a are substantially parallel with a resin surface 1a of the resin case 1. As a result, the inner surface 2d is positioned on a plane substantially the same as the resin surface 1a. However, there is a small gap between the inner surface 2d and the resin surface 1a. The hole 1b is formed to be larger than the dimensions of the nut 7 in consideration of the capability of assembling the hole 1b and the nut 7, wherein there is a gap G between inner wall surfaces of the hole 1b and the nut 7 embedded in the hole 1b. 
A busbar (not shown) being a conductor for outwardly connecting is in contact with the outer surface 2c of the end 2a on the outwardly connecting side, the bolt is screwed to the nut 7 through a hole 2f for a bolt in the end 2a on the outwardly connecting side to fix the busbar (not shown) to the end 2a on the outwardly connecting side. The bolt can be tightened with a relatively large torque for example, 12N-m and so on with respect to a bolt size M6. When mounted on a vehicle, oscillation by a relatively large acceleration, for example 20G, is applied to the resin case 1.
The conventional semiconductor device for electric power was constructed as described above. Therefore, when the nut 7 was tightened with a large torque, because there was the gap G between the nut and the hole 1b formed in the resin case 1 around the nut 7, a corner of the nut 7 was in contact with a wall surface of the hole 1b so as to cause high stress, and therefore the resin case 1 was destroyed. Further, the end 2a on the outwardly connecting side was supported by the bending portion 2e, being an extension of the bending portion 2e, there was a problem that the bending portion 2e was deformed by buckling a large torque. Further, there was a problem that the main circuit terminal was broken at the bending portion 2e by a fatigue failure caused by vibration occurred by a large acceleration applied for a long time.
As a countermeasure to the above-mentioned problems, proposed was the use of a nut 7 molded integrally with a resin case 1 so that a contact surface between an end 2a on an outwardly connecting side and that an inner surface 2d was exposed to avoid a clearance between the nut 7, and the molded resin. In this proposal, however, although a problem that the resin case 1 was broken could be solved, since a tip of the end 2a on the outwardly connecting side was exposed from a bending portion 2e, the above-mentioned buckling problem and breaking problem of the bending portion 2e caused by a fatigue failure could not be solved.
It is an object of the present invention to solve the above-mentioned problems inherit in the conventional technique and to provide a semiconductor device for electric power having a main circuit terminal which can bear tightening with a large torque and oscillation by a large acceleration.
According to a first aspect of the present invention, there is provided a semiconductor device for electric power comprising: a main circuit terminal sealed by a resin and having an end on an outwardly connecting side, bent so to be parallel with a resin surface of the sealing resin; a nut being in contact with an inner surface of the end on the outwardly connecting side; and a bolt screwed to the nut for fixing an outwardly connecting conductor in contact with an outer surface of the end on the outwardly connecting side, wherein the end on the inwardly connecting side is embedded in an inside portion of the sealing resin so that the outer surface of the end on the outwardly connecting side and the resin surface around the end are in the same planes, or that the outer surface protrudes a bit from the resin surface to make the outer surface expose from the resin surface, and the main circuit terminal and the nut are monolithically molded.
According to a second aspect of the present invention, there is provided a semiconductor device for electric power comprising: a main circuit terminal inserted in a resin case and having an end on an outwardly connecting side, bent so as to be in parallel with a resin surface, from which the main circuit terminal of the resin case protrudes; a nut being in contact with an inner surface of the end on the outwardly connecting side; and a bolt screwed to the nut to fix an outwardly connecting conductor so as to be in contact with an outer surface of the end on the outwardly connecting side, wherein the end on the outwardly connecting side is embedded in the resin case so that the outer surface of the end on the outwardly connecting side and the resin surface around the end on the outwardly connecting side are in the same plane or the outer surface protrudes a bit from the resin surface to expose the outer surface from the resin surface, and the main circuit terminal, the nut, and the resin case are monolithically molded.
According to a third aspect of the present invention, there is provided the semiconductor device for electric power, wherein the nut is a flange nut having a flange, and a surface of the flange is in contact with an inner surface of the end on the outwardly connecting side.
According to a fourth aspect of the present invention, there is provided a semiconductor device for electric power, wherein a radius of a bending portion of the end of the main circuit terminal on the outwardly connecting side is 2 mm or more on the outer surface, and the main circuit terminal is plated after bending.
According to a fifth aspect of the present invention, there is provided the semiconductor device for electric power, further comprising: an anchor formed in at least a part of an outer periphery of the end of the main circuit terminal on the outwardly connecting side so as to protrude from the outer periphery and turn toward an inside of the resin.
According to a sixth aspect of the present invention, there is provided the semiconductor device for electric power, wherein at least one of a surface shaped which is C-shaped, a slanted surface, and a step is formed on an outer surface side of an edge of the outer surface in the end of the main circuit terminal on the outwardly connecting side, and the outer surface side of the edge of the outer periphery is covered by the resin.
According to a seventh aspect of the present invention, there is provided the semiconductor device for electric power, wherein at least a part of the end of the main circuit terminal on the outwardly connecting side in the vicinity of the edge of the outer periphery other than the bending portion on the outer surface is covered by the resin protruding from the outer surface.